Messages in this thread Patch in this message | | | Date | Tue, 25 Feb 2020 23:47:34 +0100 | From | Thomas Gleixner <> | Subject | [patch 15/15] x86/entry: Use return_from_exception() |
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Replace the ASM return from exception checks for user mode and kernel mode return with the new C function and invoke this from the idtentry_exit() helper for all regular exceptions and IST exceptions which hit user mode.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> --- arch/x86/entry/common.c | 13 +++---------- arch/x86/entry/entry_32.S | 25 ++++--------------------- arch/x86/entry/entry_64.S | 25 ++----------------------- arch/x86/include/asm/idtentry.h | 7 +++++-- 4 files changed, 14 insertions(+), 56 deletions(-)
--- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -196,7 +196,7 @@ static void exit_to_usermode_loop(struct } /* Called with IRQs disabled. */ -static inline void __prepare_exit_to_usermode(struct pt_regs *regs) +static inline void prepare_exit_to_usermode(struct pt_regs *regs) { struct thread_info *ti = current_thread_info(); u32 cached_flags; @@ -241,13 +241,6 @@ static inline void __prepare_exit_to_use mds_user_clear_cpu_buffers(); } -__visible inline notrace void prepare_exit_to_usermode(struct pt_regs *regs) -{ - __prepare_exit_to_usermode(regs); - trace_hardirqs_on(); -} -NOKPROBE_SYMBOL(prepare_exit_to_usermode); - #define SYSCALL_EXIT_WORK_FLAGS \ (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \ _TIF_SINGLESTEP | _TIF_SYSCALL_TRACEPOINT) @@ -299,7 +292,7 @@ static void syscall_slow_exit_work(struc syscall_slow_exit_work(regs, cached_flags); local_irq_disable(); - __prepare_exit_to_usermode(regs); + prepare_exit_to_usermode(regs); /* Return to user space enables interrupts */ trace_hardirqs_on(); } @@ -429,7 +422,7 @@ static __always_inline long do_fast_sysc /* User code screwed up. */ local_irq_disable(); regs->ax = -EFAULT; - __prepare_exit_to_usermode(regs); + prepare_exit_to_usermode(regs); return 0; /* Keep it simple: use IRET. */ } --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -862,15 +862,10 @@ SYM_CODE_START(ret_from_fork) SYM_CODE_END(ret_from_fork) /* - * Return to user mode is not as complex as all this looks, - * but we want the default path for a system call return to - * go as quickly as possible which is why some of this is - * less clear than it otherwise should be. + * C code already did all preparatory work (prepare_exit_to_usermode or + * kernel preemption) so this just has to select the proper return path. */ - - # userspace resumption stub bypassing syscall exit tracing SYM_CODE_START_LOCAL(ret_from_exception) -ret_from_intr: #ifdef CONFIG_VM86 movl PT_EFLAGS(%esp), %eax # mix EFLAGS and CS movb PT_CS(%esp), %al @@ -884,9 +879,6 @@ SYM_CODE_START_LOCAL(ret_from_exception) #endif cmpl $USER_RPL, %eax jb restore_all_kernel # not returning to v8086 or userspace - - movl %esp, %eax - call prepare_exit_to_usermode jmp restore_all_switch_stack SYM_CODE_END(ret_from_exception) @@ -1125,15 +1117,6 @@ SYM_FUNC_START(entry_INT80_32) INTERRUPT_RETURN restore_all_kernel: -#ifdef CONFIG_PREEMPTION - cmpl $0, PER_CPU_VAR(__preempt_count) - jnz .Lno_preempt - testl $X86_EFLAGS_IF, PT_EFLAGS(%esp) # interrupts off (exception path) ? - jz .Lno_preempt - call preempt_schedule_irq -.Lno_preempt: -#endif - TRACE_IRQS_IRET PARANOID_EXIT_TO_KERNEL_MODE BUG_IF_WRONG_CR3 RESTORE_REGS 4 @@ -1247,7 +1230,7 @@ SYM_CODE_START_LOCAL(asm_\cfunc) movl PT_ORIG_EAX(%esp), %edx /* get the vector from stack */ movl $-1, PT_ORIG_EAX(%esp) /* no syscall to restart */ call \cfunc - jmp ret_from_intr + jmp ret_from_exception SYM_CODE_END(asm_\cfunc) .endm @@ -1294,7 +1277,7 @@ SYM_FUNC_START(exc_xen_hypervisor_callba #ifndef CONFIG_PREEMPTION call xen_maybe_preempt_hcall #endif - jmp ret_from_intr + jmp ret_from_exception SYM_FUNC_END(exc_xen_hypervisor_callback) /* --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -701,10 +701,6 @@ SYM_CODE_END(\asmsym) #include <asm/idtentry.h> SYM_CODE_START_LOCAL(common_interrupt_return) - /* Interrupt came from user space */ -.Lretint_user: - mov %rsp,%rdi - call prepare_exit_to_usermode SYM_INNER_LABEL(swapgs_restore_regs_and_return_to_usermode, SYM_L_GLOBAL) #ifdef CONFIG_DEBUG_ENTRY @@ -746,24 +742,7 @@ SYM_INNER_LABEL(swapgs_restore_regs_and_ SWAPGS INTERRUPT_RETURN - /* Returning to kernel space */ -retint_kernel: -#ifdef CONFIG_PREEMPTION - /* Interrupts are off */ - /* Check if we need preemption */ - btl $9, EFLAGS(%rsp) /* were interrupts off? */ - jnc 1f - cmpl $0, PER_CPU_VAR(__preempt_count) - jnz 1f - call preempt_schedule_irq -1: -#endif - /* - * The iretq could re-enable interrupts: - */ - TRACE_IRQS_IRETQ - SYM_INNER_LABEL(restore_regs_and_return_to_kernel, SYM_L_GLOBAL) #ifdef CONFIG_DEBUG_ENTRY /* Assert that pt_regs indicates kernel mode. */ @@ -1167,8 +1146,8 @@ SYM_CODE_START_LOCAL(error_exit) UNWIND_HINT_REGS DEBUG_ENTRY_ASSERT_IRQS_OFF testb $3, CS(%rsp) - jz retint_kernel - jmp .Lretint_user + jz restore_regs_and_return_to_kernel + jmp swapgs_restore_regs_and_return_to_usermode SYM_CODE_END(error_exit) /* --- a/arch/x86/include/asm/idtentry.h +++ b/arch/x86/include/asm/idtentry.h @@ -41,11 +41,14 @@ static __always_inline void idtentry_ent /** * idtentry_exit - Prepare returning to low level ASM code * - * Disables interrupts before returning + * Invokes return_from_exception() which disables interrupts + * and handles return to user mode work and kernel preemption. + * This function returns with interrupts disabled and the + * hardirq tracing state updated. */ static __always_inline void idtentry_exit(struct pt_regs *regs) { - local_irq_disable(); + return_from_exception(regs); } /**
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